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Adding (blending) two images using OpenCV {#tutorial_adding_images}
=========================================
Goal
----
In this tutorial you will learn:
- what is *linear blending* and why it is useful;
- how to add two images using @ref cv::addWeighted
Theory
------
@note
The explanation below belongs to the book [Computer Vision: Algorithms and
Applications](http://szeliski.org/Book/) by Richard Szeliski
From our previous tutorial, we know already a bit of *Pixel operators*. An interesting dyadic
(two-input) operator is the *linear blend operator*:
\f[g(x) = (1 - \alpha)f_{0}(x) + \alpha f_{1}(x)\f]
By varying \f$\alpha\f$ from \f$0 \rightarrow 1\f$ this operator can be used to perform a temporal
*cross-dissolve* between two images or videos, as seen in slide shows and film productions (cool,
eh?)
Source Code
-----------
Download the source code from
[here](https://github.com/opencv/opencv/tree/master/samples/cpp/tutorial_code/core/AddingImages/AddingImages.cpp).
@include cpp/tutorial_code/core/AddingImages/AddingImages.cpp
Explanation
-----------
-# Since we are going to perform:
\f[g(x) = (1 - \alpha)f_{0}(x) + \alpha f_{1}(x)\f]
We need two source images (\f$f_{0}(x)\f$ and \f$f_{1}(x)\f$). So, we load them in the usual way:
@snippet cpp/tutorial_code/core/AddingImages/AddingImages.cpp load
**warning**
Since we are *adding* *src1* and *src2*, they both have to be of the same size (width and
height) and type.
-# Now we need to generate the `g(x)` image. For this, the function @ref cv::addWeighted comes quite handy:
@snippet cpp/tutorial_code/core/AddingImages/AddingImages.cpp blend_images
since @ref cv::addWeighted produces:
\f[dst = \alpha \cdot src1 + \beta \cdot src2 + \gamma\f]
In this case, `gamma` is the argument \f$0.0\f$ in the code above.
-# Create windows, show the images and wait for the user to end the program.
@snippet cpp/tutorial_code/core/AddingImages/AddingImages.cpp display
Result
------
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